The present invention relates to an apparatus for controlling the position of a marine propulsion device and, more particularly, to an apparatus for providing separate trim, tilt and lift movements for a transom extension mounting assembly carrying an outboard motor.
Marine propulsion devices, such as outboard motors and stern drives, are supported from the boat transom by a drive mounting assembly. Various types of drive mounting assemblies are known, as for example a transom bracket for mounting an outboard motor directly on a boat transom or a gimbal ring assembly for similarly mounting a stern drive unit directly to the transom. Typically a drive unit mounted directly on a transom may be trimmed by pivoting it about a generally horizontal axis to position the propeller and optimize thrust with respect to the plane of the boat. However, the vertical position of the drive unit cannot typically be changed beyond the somewhat limited amount which results from the trimming operation. Therefore, the drive unit is typically mounted in a compromise position at a fixed height which will provide the best performance. Another type of drive mounting assembly is one which is capable of selectively supporting an outboard motor in either a raised or a lowered position aft of the boat transom. Many of these transom extension types of mounting assemblies are of the general type which include a pivotally connected quadrilateral linkage. Recently, transom extension mounting assemblies have become increasingly popular on high performance boats powered by outboard motors, including bass boats, where a lower position of the motor improves initial boat acceleration, and a higher position enhances top speed by reducing gear case drag. Additionally, a higher motor position reduces draft, thereby enhancing shallow water operation. It is further known that relocating the motor aft of the transom improves the handling characteristics of most boats at high speeds. These devices also allow the boat to have a higher transom for improved safety in following wave conditions and they allow boat builders to manufacture a common hull and transom design for both outboard and stern drive applications.
Examples of transom extension mounting assemblies for outboard motors which support the motor spaced from the boat transom are disclosed in the following U.S. Pat. Nos. 2,782,744; 3,990,660; 4,013,249; 4,168,818; 4,673,358; and 4,682,961. The first four of the foregoing patents disclose apparatus which is utilized to raise the motor vertically and the latter two patents describe apparatus which is utilized to trim the propeller and tilt the motor up and out of the water about a generally horizontal axis.
U.S. Pat. No. 4,490,120 shows a hydraulic system for trimming and tilting an outboard motor in which a single electric motor-driven pump powers a pair of hydraulic trim cylinders and a single hydraulic tilt cylinder. U.S. Pat. No. 4,050,359 describes a system in which a pair of hydraulic cylinders provides combined trim and tilt functions, the latter to pivot the outboard motor to its highest position as to remove it from the water or trailering.
U.S. patent application Ser. No. 092,168, filed Sept. 2, 1987; Ser. No. 100,216, filed Sept. 23, 1987; and Ser. No. 103,508, filed Oct. 1, 1987, all of which are assigned to the assignee of this application, disclose outboard motor transom extension mounting assemblies which utilize a quadrilateral linkage arrangement to raise and lower the motor with respect to the transom. The quadrilateral linkage comprises four pivotally connected links forming a collapsible linkage the movement of which effects vertical movement of the motor. In particular, pending application Ser. No. 103,508 discloses a quadrilateral transom mounting bracket with opposite arms of unequal length, the effect of which is to provide limited trimming movement of the motor simultaneously with the lift movement.
In summary, the prior art discloses apparatus for providing a trim or trim/tilt function for outboard motors which are attached directly to the transom or which are spaced therefrom on transom extension mounting assemblies. Further, transom extension mounting assemblies for outboard motors are known which provide solely a lift function or solely a trim/tilt function. Finally, in the commonly owned pending application Ser. No. 103,508 identified above, a transom extension assembly providing primarily a lift function also provides a simultaneous trim function.
However, it would be desirable to have a transom extension mounting assembly for an outboard motor in which trim, tilt and lift functions could be performed and controlled independently. Further, such an apparatus utilizing a single power source would be most desirable.